1. Field of the Art
This invention relates generally to an ultrasound endoscope to be introduced into a body cavity of a patient for making ultrasound scans of internal body tissues in addition to an endoscopic examination, and more particularly to an ultrasound endoscope which is so arranged as to guarantee safe use of a puncture instrument or similar treating instruments.
2. Prior Art
Endoscopes and ultrasound probes are in wide use especially in medical fields for examining intracavitary portions for diagnostic or therapeutical purposes. An endoscopes is used mainly for examination of surface conditions of intracavitary walls, while an ultrasound probe is used for scanning internal body tissues. Besides, there have also been in wide use the so-called ultrasound endoscopes which are equipped with an ultrasound scanning system along with an endoscopic observation system. More particularly, ultrasound endoscopes are generally provided with an endoscopic or optical observation system, including an illuminating or lighting system and an image pickup system which are incorporated into a distal end portion of an elongated flexible insertion instrument, and an ultrasound scan system including an ultrasound transducer which is also incorporated into the distal end portion of the insertion instrument. It is usually the case that the distal end of the flexible insertion instrument is constituted by a rigid casing structure, and accommodates an endoscopic observation system and an ultrasound scan system side by side in the radial direction. In this regard, in most cases, an ultrasound scanner including an ultrasound transducer is located forward of an endoscopic image pickup portion of the endoscopic observation system. In addition, in order to introduce the endoscopic insertion instrument into a body cavity in compliance with the shape of a duct or a path of insertion which may contain bends on the way as in the case of peroral insertion, an angle section or a flexible joint is attached to the rigid distal end casing structure which constitutes a rigid distal end section of the endoscopic insertion instrument.
When a diseased portion is detected in internal body tissues as a result of an examination by an ultrasound endoscope as described above, it is desirable for the detected diseased portion to be treated on the spot by way of the inserted ultrasound endoscope. In order to permit treatments within or from a body cavity, ultrasound endoscopes are usually provided with a biopsy channel or instrument channel coextensively within an endoscopic insertion instrument for insertion therethrough of a treating instrument such as forceps, high frequency treating instrument or the like. A treating instrument of this sort is extended into a patient's body cavity through an exit opening at the distal end of the endoscopic insertion instrument. For accurate manipulation of the treating instrument within a body cavity, it is desirable for the operator to be able to constantly monitor and confirm from outside the position and posture of the treating instrument which is projected into the body cavity through the endoscopic insertion instrument. This is possible with ultrasound endoscopes which are equipped with an ultrasound scan system, in contrast to ordinary endoscopes which do not. For instance, a puncture instrument with a sharp-pointed puncture needle can be monitored from outside and manipulated accurately as it is projected into a body cavity from an endoscopic biopsy channel and penetrated into a target portion for injection of a medicinal liquid or for aspiration of a bleeding site.
For monitoring purposes, a treating instrument which is projected into a body cavity through an opening at the distal end of an endoscopic biopsy channel should be firstly within a view field of an image pickup of an endoscopic observation system, and, after penetration into an intracavitary wall or internal organ, within a view field of an ultrasound scan system. For this purpose, the distal end opening of the endoscopic biopsy channel needs to be located between an image pickup window of an endoscopic observation system and a scanner of an ultrasound examination system.
More particularly, in order to have a puncture instrument invariably within the view fields of both endoscopic observation system and ultrasound examination system, it is conceivable to arrange an ultrasound endoscope in the manner as follows. Firstly, the endoscopic observation system can employ an oblique view type image pickup having a view field in an angular direction relative to the axis of the insertion instrument of the ultrasound endoscope, in combination with an ultrasound scanning system of an electronic scan type which has a large number of ultrasound transducer elements arranged in the axial direction of the endoscopic insertion instrument in order to secure a wide scanning range which substantially overlaps the view field of the endoscopic image pickup. In such a case, the distal end opening of the biopsy channel on the endoscopic insertion instrument is arranged such that a treating instrument can protrude into a body cavity in a direction parallel with or at a shallow angle with the center axis of the view field of the endoscopic image pickup portion.
Regarding the treating instrument, a puncture instrument usually includes a puncture needle member consisting of a rigid pipe of a certain length. On the other hand, the endoscopic insertion instrument has a flexible structure except the distal end section which is constituted by a rigid casing structure. Normally, angle section or a flexible joint is interposed between the rigid distal end section and the flexible main body of the insertion instrument, allowing to turn the direction of the view field of an endoscopic image pickup on the rigid distal end section through a large angle. Therefore, the endoscopic insertion instrument which has been introduced into a body cavity of a patient may have the rigid distal end section in such an angularly bent form as to completely block passage of a rigid needle portion of a puncture instrument. In order to avoid this, it has been the general practice to place a treating instrument like a puncture needle into the endoscopic biopsy channel before insertion into a body cavity of a patient. Since the needle of the puncture instrument is rigid and sharp-pointed, it should always be retained in a retracted position within the endoscopic biopsy channel and kept out of contact with intracavitary walls except when it is driven forward for penetration into an intracavitary wall or into an internal organ which needs a treatment.
To cope with a deep penetration, the puncture instrument needs to have a rigid needle portion of an increased length. On the other hand, from the standpoint of moving the puncture instrument back and forth or in projecting and retracting directions within the biopsy channel of an endoscopic insertion instrument which has a rigid fore distal end section connected to its fore end through an angle section or a flexible joint, it is more convenient to locate the rigid puncture needle substantially in the rigid fore distal end section, and to locate a flexible tube, which is connected to the proximal end of the rigid puncture needle, in the flexible section of the endoscopic insertion instrument rearward of the angle section. Nevertheless, the rigid distal end section of the endoscopic insertion instrument is normally required to have as small an axial length as possible for the purpose of ensuring smooth introduction into a body cavity and at the same time for lessening the pains on the part of the patient. It follows that, in case the puncture needle has an increased length, it might become difficult to accommodate the puncture needle within the length of the inflexible rigid distal end section of the endoscopic insertion instrument. Especially, in the case of an ultrasound endoscope having a bent pipe connected to the fore end portion of a biopsy channel as a shunt passage for projecting a treating instrument obliquely into the view field of an oblique view type endoscopic image pickup, a proximal end portion of the rigid puncture needle is necessarily located partly in the bent portion of the shunt pipe in a forcibly bent form.
Taking the foregoing situations into consideration, the sharp-pointed end of a long puncture needle has to be positioned as closely to the distal end opening of the endoscopic biopsy channel as possible. When the angle section of the endoscopic insertion instrument is flexed to turn the rigid distal end section into the direction of a target, however, the puncture needle could be accidentally projected out of the biopsy channel of the endoscopic insertion instrument, depending upon the turning angle. Further, a proximal end portion of the puncture instrument, which is led out of the endoscopic insertion instrument through an opening at the proximal end of the biopsy channel, is manipulated by an operator to push the puncture instrument in the forward direction for projecting the puncture needle into a penetrating position. The sharp-pointed fore end of the puncture needle in a retracted rest position, however, could be instantly projected out of the biopsy channel when the puncture needle is accidentally pushed forward even in a slight degree. In this regard, according to the prior art, it has been difficult to monitor the position of the sharp-pointed fore end of the puncture needle within the view field of an endoscopic image pickup until the puncture instrument is projected over a certain length from the distal opening of the endoscopic biopsy channel. Namely, it has thus far been difficult to check, within the view field of the endoscopic image pickup, the position of the sharp-pointed end of the puncture instrument in or in the vicinity of the distal opening of the biopsy channel. Therefore, even if the sharp-pointed end of the puncture needle is slightly projected from the distal opening of the biopsy channel for some reason, in many cases this cannot be recognized by the operator.
From the standpoint of safe use or safe treatment, a puncture instrument, when at rest, should be retracted sufficiently to a deep position within the biopsy channel at least while the endoscopic insertion instrument is disposed in a body cavity of a patient. However, because of a short axial length of the rigid distal end section of the endoscopic insertion instrument, it is often found difficult to retract the rigid puncture needle smoothly into and out of the endoscopic biopsy channel unless it is reduced in length to such an extent as would make deep penetrations infeasible.